Today my 2001 1500 5.9 L (172,000 miles) popped out of 4WD going up a long (~2-miles), steep mountain (rough dirt road, some mud). I put it back in, and it popped out again (with grinding). I put it back in 2WD on shifter and it would not move uphill.. I thought I was dead in the water and put it in reverse, backed down most of mountain. Turned around to limp home. Tried to put it in 1st to slow down and grinded and slipped out (with grinding). Left it in Drive and it worked (but had to use brakes down the hill and they got hot). Over a decade ago I had the OEM transmission replaced with another OEM transmission. This transmission has slipped before at highway speeds on the interstate while pulling a horse trailer years ago, but I just stopped hauling with it. Was fine for day to day use.
What do you think? Where should I start? Vacuum line, Transfer Case, or Transmission?
Thanks!
Teresa.

 

When you say "popped out" did the 4X4 light go out? Do you have wild vents?

 

Worn range fork in t-case. Order a rebuild kit.

Although FIRST check motor mounts and the shift linkage itself. If those appear tight, it's your range fork and possibly your 4wd fork, too. The former selects hi/low/neutral and the latter just elects to power the front output, or not.

edit: rebuild kits will include shift fork PADS but not the forks themselves. If you can wait, open the case and figure out exactly what you need, then order parts. I'd probably get a chain, too.

 

Hi,
The 4WD light went out and the shifter moved out of 4wd. I don't know what wild vents are.

 

I googled wild vents and found a description and my truck probably does have them. The AC and heater air does switch around. I call it character.
I will try the check valves first.
Thanks for your help.

 

Thanks! I will start poking around. Luckily this is not my daily driver.

 

OP is getting stuck in N and experiencing grinding noises.

99% chance this is NOT a vacuum issue. The front CAD can theoretically grind a little, but it can never in any way affect the engagement of high range, low range or neutral. Worst case with a vacuum problem you select 4hi and effectively get 2hi, or select 4lo and get 2lo. Neutral is always neutral, which is no man's land between direct drive and the planetaries in the t-case (note I'm not speaking of N in the transmission which is a very separate thing)

 

I tend to shut the engine off if I get the t-case into neutral.... easier to shift that way.